Levo-ornidazole (1-(3-chloro-2-S-(−)-hydroxypropyl)-2-methyl-5-nitroimidazole) is the levo-isomer of ornidazole (CAS 16773-42-5). As a nitroimidazole derivative, ornidazole is a powerful anti-anaerobic bacteria and anti-parasite infection agent, and also as the newly developed third-generation of nitroimidazole derivative next to the 2-methyl-5-nitro-1H-Imidazole-1-ethanol, ornidazole exhibits higher therapeutical efficacy, shorter clinical course, better tolerance, and wider in-vivo distribution. The anti-microorganisms effect of ornidazole is promoted by the reduction of nitro group of its molecule to amino group under anaerobic environment, or by the formation of free radical followed by interaction with the cellular components, and caused to the death of microorganisms. Ornidazole racemate is the active ingredient in commercial ornidazole agents. Anti-anaerobic bacteria activity of ornidazole has been widely reported in clinical practice, such as the clinical and experimental study of ornidazole for the treatment of oral anaerobic infections (see Chinese Journal of Nosocomiology. 2004. 14 (3). -325-327); the clinical effects of ornidazole injection in the treatment of gynecological anaerobic infections (see Chinese Journal of New Drugs. 2004. 13 (2).-158-160); analysis of ornidazole injection in the treatment of 56 cases of senile diabetic foot anaerobic infections (the Chinese Medical Journal Writing. 2004. 11 (10).-843-844). Ornidazole exhibits good therapeutical efficacy in the treatment of anaerobic bacteria infections, but there are also some adverse effects, primarily expressed as central Inhibitory effects. In China, there is a patent application (CN 1400312A) regarding the separation of racemic ornidazole into L- and D-ornidazole by means of enzymatic resolution, however, comparative studies on the pharmacology and pharmacodynamics among L- and D-ornidazole and racemic ornidazole has not been published yet.